Throughout the various stages of plasma processing, such as semiconductor or display manufacturing, etc., critical process parameters may vary significantly. Processing conditions change over time with the slightest changes in critical process parameters creating undesirable results. Small changes can easily occur in the composition or pressure of an etch gas, process chamber, or substrate temperature. As such, plasma processing facilities require constant monitoring. Even under conditions expected to yield nominally the same results, the development of the depositions for example of insulating (or conducting) layers on the fixtures of the plasma processing facility alter the electrical impedance of the processing facility and, hence, alter the existing electrical configuration by which power is coupled into the plasma facility. As such, the plasma densities and plasma uniformities change with time (i.e., age) despite the consistency of input parameters.
During the manufacture of semiconductor ICs, monitoring and controlling process parameters are critical for acquiring the highest IC product yield and quality. For example, the precise control of etch feature critical dimensions is critical in the damascene structure process that is utilized for forming IC wiring levels and interconnect structures through inter- and intra-level dielectric layers, as well as gate contacts. Yet, the required process control is hampered by the above noted changes occurring within the plasma processing facility.
Conventionally, after-the-effect observations of the resultant etch process or resultant etch structure are used as a best guest basis to alter the process control model in an attempt to “correct” the process. Such after-the-effect approaches to process control waste product as the process model is corrected. Further, such after-the-effect changes are not designed to predict changes to the process model.